Re: [PATCH 39/43] xfs: support write life time based data placement

Darrick J. Wong
2025-02-12T00:27:27Z

On Thu, Feb 06, 2025 at 07:44:55AM +0100, Christoph Hellwig wrote:
> From: Hans Holmberg <hans.holmberg@wdc.com>
>
> Add a file write life time data placement allocation scheme that aims to
> minimize fragmentation and thereby to do two things:
>
> a) separate file data to different zones when possible.
> b) colocate file data of similar life times when feasible.
>
> To get best results, average file sizes should align with the zone
> capacity that is reported through the XFS_IOC_FSGEOMETRY ioctl.
>
> For RocksDB using leveled compaction, the lifetime hints can improve
> throughput for overwrite workloads at 80% file system utilization by
> ~10%.

The code changes look mostly ok, but how does it do at 40% utilization?
99%? Does it reduce the amount of relocation work that the gc must do?

--D

> Lifetime hints can be disabled using the nolifetime mount option.
>
> Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> fs/xfs/xfs_mount.h | 2 +
> fs/xfs/xfs_super.c | 15 +++++
> fs/xfs/xfs_zone_alloc.c | 130 +++++++++++++++++++++++++++++++++++-----
> fs/xfs/xfs_zone_gc.c | 4 +-
> fs/xfs/xfs_zone_priv.h | 9 ++-
> 5 files changed, 141 insertions(+), 19 deletions(-)
>
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index 6c5757f6e4ef..7c7fd94375c1 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -363,6 +363,7 @@ typedef struct xfs_mount {
> #define XFS_FEAT_ZONED (1ULL << 29) /* zoned RT device */
>
> /* Mount features */
> +#define XFS_FEAT_NOLIFETIME (1ULL << 47) /* disable lifetime hints */
> #define XFS_FEAT_NOATTR2 (1ULL << 48) /* disable attr2 creation */
> #define XFS_FEAT_NOALIGN (1ULL << 49) /* ignore alignment */
> #define XFS_FEAT_ALLOCSIZE (1ULL << 50) /* user specified allocation size */
> @@ -418,6 +419,7 @@ __XFS_HAS_FEAT(large_extent_counts, NREXT64)
> __XFS_HAS_FEAT(exchange_range, EXCHANGE_RANGE)
> __XFS_HAS_FEAT(metadir, METADIR)
> __XFS_HAS_FEAT(zoned, ZONED)
> +__XFS_HAS_FEAT(nolifetime, NOLIFETIME)
>
> static inline bool xfs_has_rtgroups(const struct xfs_mount *mp)
> {
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index b59d7349dbd2..01166e519413 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -111,6 +111,7 @@ enum {
> Opt_prjquota, Opt_uquota, Opt_gquota, Opt_pquota,
> Opt_uqnoenforce, Opt_gqnoenforce, Opt_pqnoenforce, Opt_qnoenforce,
> Opt_discard, Opt_nodiscard, Opt_dax, Opt_dax_enum, Opt_max_open_zones,
> + Opt_lifetime, Opt_nolifetime,
> };
>
> static const struct fs_parameter_spec xfs_fs_parameters[] = {
> @@ -156,6 +157,8 @@ static const struct fs_parameter_spec xfs_fs_parameters[] = {
> fsparam_flag("dax", Opt_dax),
> fsparam_enum("dax", Opt_dax_enum, dax_param_enums),
> fsparam_u32("max_open_zones", Opt_max_open_zones),
> + fsparam_flag("lifetime", Opt_lifetime),
> + fsparam_flag("nolifetime", Opt_nolifetime),
> {}
> };
>
> @@ -184,6 +187,7 @@ xfs_fs_show_options(
> { XFS_FEAT_LARGE_IOSIZE, ",largeio" },
> { XFS_FEAT_DAX_ALWAYS, ",dax=always" },
> { XFS_FEAT_DAX_NEVER, ",dax=never" },
> + { XFS_FEAT_NOLIFETIME, ",nolifetime" },
> { 0, NULL }
> };
> struct xfs_mount *mp = XFS_M(root->d_sb);
> @@ -1091,6 +1095,11 @@ xfs_finish_flags(
> "max_open_zones mount option only supported on zoned file systems.");
> return -EINVAL;
> }
> + if (mp->m_features & XFS_FEAT_NOLIFETIME) {
> + xfs_warn(mp,
> +"nolifetime mount option only supported on zoned file systems.");
> + return -EINVAL;
> + }
> }
>
> return 0;
> @@ -1477,6 +1486,12 @@ xfs_fs_parse_param(
> case Opt_max_open_zones:
> parsing_mp->m_max_open_zones = result.uint_32;
> return 0;
> + case Opt_lifetime:
> + parsing_mp->m_features &= ~XFS_FEAT_NOLIFETIME;
> + return 0;
> + case Opt_nolifetime:
> + parsing_mp->m_features |= XFS_FEAT_NOLIFETIME;
> + return 0;
> default:
> xfs_warn(parsing_mp, "unknown mount option [%s].", param->key);
> return -EINVAL;
> diff --git a/fs/xfs/xfs_zone_alloc.c b/fs/xfs/xfs_zone_alloc.c
> index ab3f46dbbc01..e8ff9788036e 100644
> --- a/fs/xfs/xfs_zone_alloc.c
> +++ b/fs/xfs/xfs_zone_alloc.c
> @@ -423,6 +423,7 @@ static struct xfs_open_zone *
> xfs_init_open_zone(
> struct xfs_rtgroup *rtg,
> xfs_rgblock_t write_pointer,
> + enum rw_hint write_hint,
> bool is_gc)
> {
> struct xfs_open_zone *oz;
> @@ -433,6 +434,7 @@ xfs_init_open_zone(
> oz->oz_rtg = rtg;
> oz->oz_write_pointer = write_pointer;
> oz->oz_written = write_pointer;
> + oz->oz_write_hint = write_hint;
> oz->oz_is_gc = is_gc;
>
> /*
> @@ -452,6 +454,7 @@ xfs_init_open_zone(
> struct xfs_open_zone *
> xfs_open_zone(
> struct xfs_mount *mp,
> + enum rw_hint write_hint,
> bool is_gc)
> {
> struct xfs_zone_info *zi = mp->m_zone_info;
> @@ -464,12 +467,13 @@ xfs_open_zone(
> return NULL;
>
> set_current_state(TASK_RUNNING);
> - return xfs_init_open_zone(to_rtg(xg), 0, is_gc);
> + return xfs_init_open_zone(to_rtg(xg), 0, write_hint, is_gc);
> }
>
> static struct xfs_open_zone *
> xfs_try_open_zone(
> - struct xfs_mount *mp)
> + struct xfs_mount *mp,
> + enum rw_hint write_hint)
> {
> struct xfs_zone_info *zi = mp->m_zone_info;
> struct xfs_open_zone *oz;
> @@ -486,7 +490,7 @@ xfs_try_open_zone(
> */
> zi->zi_nr_open_zones++;
> spin_unlock(&zi->zi_open_zones_lock);
> - oz = xfs_open_zone(mp, false);
> + oz = xfs_open_zone(mp, write_hint, false);
> spin_lock(&zi->zi_open_zones_lock);
> if (!oz) {
> zi->zi_nr_open_zones--;
> @@ -512,16 +516,78 @@ xfs_try_open_zone(
> return oz;
> }
>
> +/*
> + * For data with short or medium lifetime, try to colocated it into an
> + * already open zone with a matching temperature.
> + */
> +static bool
> +xfs_colocate_eagerly(
> + enum rw_hint file_hint)
> +{
> + switch (file_hint) {
> + case WRITE_LIFE_MEDIUM:
> + case WRITE_LIFE_SHORT:
> + case WRITE_LIFE_NONE:
> + return true;
> + default:
> + return false;
> + }
> +}
> +
> +static bool
> +xfs_good_hint_match(
> + struct xfs_open_zone *oz,
> + enum rw_hint file_hint)
> +{
> + switch (oz->oz_write_hint) {
> + case WRITE_LIFE_LONG:
> + case WRITE_LIFE_EXTREME:
> + /* colocate long and extreme */
> + if (file_hint == WRITE_LIFE_LONG ||
> + file_hint == WRITE_LIFE_EXTREME)
> + return true;
> + break;
> + case WRITE_LIFE_MEDIUM:
> + /* colocate medium with medium */
> + if (file_hint == WRITE_LIFE_MEDIUM)
> + return true;
> + break;
> + case WRITE_LIFE_SHORT:
> + case WRITE_LIFE_NONE:
> + case WRITE_LIFE_NOT_SET:
> + /* colocate short and none */
> + if (file_hint <= WRITE_LIFE_SHORT)
> + return true;
> + break;
> + }
> + return false;
> +}
> +
> static bool
> xfs_try_use_zone(
> struct xfs_zone_info *zi,
> - struct xfs_open_zone *oz)
> + enum rw_hint file_hint,
> + struct xfs_open_zone *oz,
> + bool lowspace)
> {
> if (oz->oz_write_pointer == rtg_blocks(oz->oz_rtg))
> return false;
> + if (!lowspace && !xfs_good_hint_match(oz, file_hint))
> + return false;
> if (!atomic_inc_not_zero(&oz->oz_ref))
> return false;
>
> + /*
> + * If we have a hint set for the data, use that for the zone even if
> + * some data was written already without any hint set, but don't change
> + * the temperature after that as that would make little sense without
> + * tracking per-temperature class written block counts, which is
> + * probably overkill anyway.
> + */
> + if (file_hint != WRITE_LIFE_NOT_SET &&
> + oz->oz_write_hint == WRITE_LIFE_NOT_SET)
> + oz->oz_write_hint = file_hint;
> +
> /*
> * If we couldn't match by inode or life time we just pick the first
> * zone with enough space above. For that we want the least busy zone
> @@ -536,14 +602,16 @@ xfs_try_use_zone(
>
> static struct xfs_open_zone *
> xfs_select_open_zone_lru(
> - struct xfs_zone_info *zi)
> + struct xfs_zone_info *zi,
> + enum rw_hint file_hint,
> + bool lowspace)
> {
> struct xfs_open_zone *oz;
>
> lockdep_assert_held(&zi->zi_open_zones_lock);
>
> list_for_each_entry(oz, &zi->zi_open_zones, oz_entry)
> - if (xfs_try_use_zone(zi, oz))
> + if (xfs_try_use_zone(zi, file_hint, oz, lowspace))
> return oz;
>
> cond_resched_lock(&zi->zi_open_zones_lock);
> @@ -552,20 +620,28 @@ xfs_select_open_zone_lru(
>
> static struct xfs_open_zone *
> xfs_select_open_zone_mru(
> - struct xfs_zone_info *zi)
> + struct xfs_zone_info *zi,
> + enum rw_hint file_hint)
> {
> struct xfs_open_zone *oz;
>
> lockdep_assert_held(&zi->zi_open_zones_lock);
>
> list_for_each_entry_reverse(oz, &zi->zi_open_zones, oz_entry)
> - if (xfs_try_use_zone(zi, oz))
> + if (xfs_try_use_zone(zi, file_hint, oz, false))
> return oz;
>
> cond_resched_lock(&zi->zi_open_zones_lock);
> return NULL;
> }
>
> +static inline enum rw_hint xfs_inode_write_hint(struct xfs_inode *ip)
> +{
> + if (xfs_has_nolifetime(ip->i_mount))
> + return WRITE_LIFE_NOT_SET;
> + return VFS_I(ip)->i_write_hint;
> +}
> +
> /*
> * Try to pack inodes that are written back after they were closed tight instead
> * of trying to open new zones for them or spread them to the least recently
> @@ -589,6 +665,7 @@ static inline bool xfs_zoned_pack_tight(struct xfs_inode *ip)
> static struct xfs_open_zone *
> xfs_select_zone_nowait(
> struct xfs_mount *mp,
> + enum rw_hint write_hint,
> bool pack_tight)
> {
> struct xfs_zone_info *zi = mp->m_zone_info;
> @@ -597,20 +674,38 @@ xfs_select_zone_nowait(
> if (xfs_is_shutdown(mp))
> return NULL;
>
> + /*
> + * Try to fill up open zones with matching temperature if available. It
> + * is better to try to co-locate data when this is favorable, so we can
> + * activate empty zones when it is statistically better to separate
> + * data.
> + */
> spin_lock(&zi->zi_open_zones_lock);
> - if (pack_tight)
> - oz = xfs_select_open_zone_mru(zi);
> + if (xfs_colocate_eagerly(write_hint))
> + oz = xfs_select_open_zone_lru(zi, write_hint, false);
> + else if (pack_tight)
> + oz = xfs_select_open_zone_mru(zi, write_hint);
> if (oz)
> goto out_unlock;
>
> /*
> * See if we can open a new zone and use that.
> */
> - oz = xfs_try_open_zone(mp);
> + oz = xfs_try_open_zone(mp, write_hint);
> if (oz)
> goto out_unlock;
>
> - oz = xfs_select_open_zone_lru(zi);
> + /*
> + * Try to colocate cold data with other cold data if we failed to open a
> + * new zone for it.
> + */
> + if (write_hint != WRITE_LIFE_NOT_SET &&
> + !xfs_colocate_eagerly(write_hint))
> + oz = xfs_select_open_zone_lru(zi, write_hint, false);
> + if (!oz)
> + oz = xfs_select_open_zone_lru(zi, WRITE_LIFE_NOT_SET, false);
> + if (!oz)
> + oz = xfs_select_open_zone_lru(zi, WRITE_LIFE_NOT_SET, true);
> out_unlock:
> spin_unlock(&zi->zi_open_zones_lock);
> return oz;
> @@ -619,19 +714,20 @@ xfs_select_zone_nowait(
> static struct xfs_open_zone *
> xfs_select_zone(
> struct xfs_mount *mp,
> + enum rw_hint write_hint,
> bool pack_tight)
> {
> struct xfs_zone_info *zi = mp->m_zone_info;
> DEFINE_WAIT (wait);
> struct xfs_open_zone *oz;
>
> - oz = xfs_select_zone_nowait(mp, pack_tight);
> + oz = xfs_select_zone_nowait(mp, write_hint, pack_tight);
> if (oz)
> return oz;
>
> for (;;) {
> prepare_to_wait(&zi->zi_zone_wait, &wait, TASK_UNINTERRUPTIBLE);
> - oz = xfs_select_zone_nowait(mp, pack_tight);
> + oz = xfs_select_zone_nowait(mp, write_hint, pack_tight);
> if (oz)
> break;
> schedule();
> @@ -709,6 +805,7 @@ xfs_zone_alloc_and_submit(
> {
> struct xfs_inode *ip = XFS_I(ioend->io_inode);
> struct xfs_mount *mp = ip->i_mount;
> + enum rw_hint write_hint = xfs_inode_write_hint(ip);
> bool pack_tight = xfs_zoned_pack_tight(ip);
> unsigned int alloc_len;
> struct iomap_ioend *split;
> @@ -726,7 +823,7 @@ xfs_zone_alloc_and_submit(
> *oz = xfs_last_used_zone(ioend);
> if (!*oz) {
> select_zone:
> - *oz = xfs_select_zone(mp, pack_tight);
> + *oz = xfs_select_zone(mp, write_hint, pack_tight);
> if (!*oz)
> goto out_error;
> }
> @@ -864,7 +961,8 @@ xfs_init_zone(
> struct xfs_open_zone *oz;
>
> atomic_inc(&rtg_group(rtg)->xg_active_ref);
> - oz = xfs_init_open_zone(rtg, write_pointer, false);
> + oz = xfs_init_open_zone(rtg, write_pointer, WRITE_LIFE_NOT_SET,
> + false);
> list_add_tail(&oz->oz_entry, &zi->zi_open_zones);
> zi->zi_nr_open_zones++;
>
> diff --git a/fs/xfs/xfs_zone_gc.c b/fs/xfs/xfs_zone_gc.c
> index 133a83b97f5f..18675466cc97 100644
> --- a/fs/xfs/xfs_zone_gc.c
> +++ b/fs/xfs/xfs_zone_gc.c
> @@ -550,7 +550,7 @@ xfs_zone_gc_select_target(
>
> ASSERT(zi->zi_nr_open_zones <=
> mp->m_max_open_zones - XFS_OPEN_GC_ZONES);
> - oz = xfs_open_zone(mp, true);
> + oz = xfs_open_zone(mp, WRITE_LIFE_NOT_SET, true);
> if (oz)
> trace_xfs_gc_zone_activate(oz->oz_rtg);
> spin_lock(&zi->zi_open_zones_lock);
> @@ -1120,7 +1120,7 @@ xfs_zone_gc_mount(
> zi->zi_nr_open_zones == mp->m_max_open_zones)
> oz = xfs_zone_gc_steal_open(zi);
> else
> - oz = xfs_open_zone(mp, true);
> + oz = xfs_open_zone(mp, WRITE_LIFE_NOT_SET, true);
> if (!oz) {
> xfs_warn(mp, "unable to allocate a zone for gc");
> error = -EIO;
> diff --git a/fs/xfs/xfs_zone_priv.h b/fs/xfs/xfs_zone_priv.h
> index f6c76d751a49..ab696975a993 100644
> --- a/fs/xfs/xfs_zone_priv.h
> +++ b/fs/xfs/xfs_zone_priv.h
> @@ -26,6 +26,12 @@ struct xfs_open_zone {
> */
> xfs_rgblock_t oz_written;
>
> + /*
> + * Write hint (data temperature) assigned to this zone, or
> + * WRITE_LIFE_NOT_SET if none was set.
> + */
> + enum rw_hint oz_write_hint;
> +
> /*
> * Is this open zone used for garbage collection? There can only be a
> * single open GC zone, which is pointed to by zi_open_gc_zone in
> @@ -100,7 +106,8 @@ struct xfs_zone_info {
>
> };
>
> -struct xfs_open_zone *xfs_open_zone(struct xfs_mount *mp, bool is_gc);
> +struct xfs_open_zone *xfs_open_zone(struct xfs_mount *mp,
> + enum rw_hint write_hint, bool is_gc);
>
> int xfs_zone_gc_reset_sync(struct xfs_rtgroup *rtg);
> bool xfs_zoned_need_gc(struct xfs_mount *mp);
> --
> 2.45.2
>
>